googleapis/mcp-toolbox · error

error processing row: %w

Error message

error processing row: %w

What it means

Returned by Source.RunSQL when iterating the N1QL query results fails: results.Next() yields an error while decoding a row via results.Row(&result). The query was accepted and rows were streaming, but reading/decoding a row failed — often a mid-stream network interruption or a server-side error surfaced during iteration.

Source

Thrown at internal/sources/couchbase/couchbase.go:133

func (s *Source) CouchbaseQueryScanConsistency() uint {
	return s.QueryScanConsistency
}

func (s *Source) RunSQL(statement string, params parameters.ParamValues) (any, error) {
	results, err := s.CouchbaseScope().Query(statement, &gocb.QueryOptions{
		ScanConsistency: gocb.QueryScanConsistency(s.CouchbaseQueryScanConsistency()),
		NamedParameters: params.AsMap(),
	})
	if err != nil {
		return nil, fmt.Errorf("unable to execute query: %w", err)
	}

	out := []any{}
	for results.Next() {
		var result json.RawMessage
		err := results.Row(&result)
		if err != nil {
			return nil, fmt.Errorf("error processing row: %w", err)
		}
		out = append(out, result)
	}
	return out, nil
}

func (r Config) createCouchbaseOptions() (gocb.ClusterOptions, error) {
	cbOpts := gocb.ClusterOptions{}

	if r.Username != "" {
		auth := gocb.PasswordAuthenticator{
			Username: r.Username,
			Password: r.Password,
		}
		cbOpts.Authenticator = auth
	}

	var clientCert, clientKey, caCert []byte

View on GitHub (pinned to 8cc6e09de2)

Solutions

1. Inspect the wrapped cause (%w) — if it is a network error, check cluster stability and connection settings
2. Add LIMIT/pagination to large queries so streams finish within timeouts
3. Increase query timeout in gocb QueryOptions or server query settings
4. Retry the query; transient stream drops during failover typically succeed on retry

out, err := source.RunSQL(ctx, statement, params)
if err != nil && strings.Contains(err.Error(), "error processing row") {
	// transient stream failure: bounded retry with backoff
	for i := 0; i < 3; i++ {
		time.Sleep(time.Duration(1<<i) * 100 * time.Millisecond)
		if out, err = source.RunSQL(ctx, statement, params); err == nil {
			break
		}
	}
}

When it happens

Trigger: The results stream breaks during iteration: connection to the query service dropped, cluster failover mid-query, query timeout/cancellation while streaming, or a row that cannot be decoded into json.RawMessage.

Common situations: Large result sets hitting streaming timeouts, unstable network to the Couchbase cluster, node failover during long queries, or query expiry (query_timeout) mid-iteration.

Related errors

• unable to execute query: %w
• errors encountered during query execution or row processing:
• errors encountered during row iteration: %w
• error reading start of json array: %w
• error decoding raw message: %w

AI-assisted analysis of googleapis/mcp-toolbox@8cc6e09de2 (2026-09-05). Data as JSON: /api/errors/be94fe12a554420e. Report an issue: GitHub.